The present invention relates to the art of injection molding, and more particularly to a self-compensating link which provides for coupling and simultaneously injecting a plurality of molds from a single injection molding machine.
When designing a mold, a decision must be made concerning how many articles are to be formed in the mold. Ordinarily, a plurality of cavities is provided so that several of the articles, such as cups or bottles, will be simultaneously formed when the injection fluid, usually plastic, is injected. Typically, the plastic will be conducted to the mold cavities through a separate manifold which is coupled to receive the plastic from the injector and conduct it into the mold cavities. The molds and manifolds are rigidly mounted and secured since the injection pressures may be as high as 20,000 psi. To prevent unwanted freezing of the plastic in the sprues and runners, it is common practice to heat the manifold continuously with electric resistance heaters in channels or cavities therein.
From time to time, the demand for a particular molded article may increase substantially. Since in many cases the injection molding machines are capable of injecting substantially more material per cycle than is required for the particular molds in use, the purchase of an entire new injection molding machine should not be necessary. Instead, a larger capacity mold should suffice. However, newly designed and tested molds and manifolds are themselves quite expensive and the lead time for designing and testing may be unacceptable. Furthermore, to replace the manifolds and molds already in use with larger capacity manifolds and molds would not only entail the effective loss of the use, and hence the economic loss of the investment cost, of existing smaller capacity molds and manifolds, but would also risk additional production delays and expenses while the larger, newly designed units are production tested and "de-bugged". There are many reasons, therefore, not to depart from those designs and/or configurations which have been found through previous experience and development efforts to be effective and serivceable, and may in some instances have even become standardized.
There is thus a need to be able to quickly increase the production capacity of injection molding machines in response to changing customer demands, while avoiding the costs and delays mentioned above. Ideally, this would use existing, tried, and proven equipment in a manner compatible with the extreme and demanding conditions found in the injection molding environment.